All swaps have a market value. Swap valuation means to determine the market value of the swap, which is the present value of one stream of payments less the present value of the other stream of payments.
To determine the market value of a swap, we replicate the swap using other instruments that produce the same cash flows. Knowing the values of these instruments, we are able to value the swap. This value can be thought of as what the swap is worth if we were to sell it to someone else. In addition, we can think of the value as what we might assign it on our balance sheet. The swap can have a positive value, making it an asset, or a negative value, making it a liability.